In addition to needing a traditional engine, a hybrid vehicle needs to use a DC power source with a certain voltage as its supplemental power source, and a battery pack formed by a plurality of serially-connected battery cells can be used as the DC power source with a certain voltage. For example, several serially-connected battery cells each having a 3.6V DC voltage can form a battery pack with 48V DC voltage.
Although a DC power source with certain voltage can be conveniently formed by a plurality of serially-connected battery cells, some drawbacks exist in using such a DC power source to supply power to hybrid vehicles. Typically, manufacturing environment and/or manufacturing process of battery cells may cause random differences for the working parameters (such as the differences of the internal resistances and non-homogeneities in chemical materials or capacity of battery cells) among battery cells in a battery pack.
During the operation of a hybrid vehicle, random environment and/or operation conditions may dynamically cause further differences for the working parameters among the battery cells in a battery pack. For example, different charging and discharging patterns in battery cell application and non-homogeneities of cell thermal distribution due to the location of the cells in a battery pack (or module) may further aggravate the non-uniformity of the battery cells in a battery pack.
When differences of working parameters among the battery cells in a battery pack become too unbalanced, the battery back may not be able to properly operate a hybrid vehicle. For example, some of the battery cells in a battery pack may overheat; or the voltage differences among the battery cells in a battery pack become too large; or the battery pack may be unable to provide sufficient current to meet the instant operation needs of a hybrid vehicle. Under these fault conditions, the battery pack is unable to operate a hybrid vehicle properly.
Therefore, it is desirable to provide a battery pack control system to enable a battery pack, which is formed by a plurality of serially-connected battery cells, to properly, effectively and efficiently supply DC power source to hybrid vehicles.
It is also desirable to provide a battery structure that can be used to more efficiently manufacture a battery, which includes a plurality of serially-connected battery cells, with efficiency to assemble, high quality and low costs.